Development of the Proximal-Anterior Skeletal Elements in the Mouse Hindlimb Is Regulated by a Transcriptional and Signaling Network Controlled by .

The vertebrate limb serves as an experimental paradigm to study mechanisms that regulate development of the stereotypical skeletal elements. In this study, we simultaneously inactivated using and in mouse embryos, and found that their combined function regulates development of the proximal-anterior skeletal elements in hindlimbs. The ; double knockout exhibits severe defects in the femur, tibia, and anterior digits, distinct defects compared to other allelic series of ; We found that regulates expression prior to hindlimb outgrowth. Further expression analysis indicated that genes and GLI3 are severely downregulated in the ; double knockout hindlimb bud. In contrast, PLZF expression is reduced but detectable in ; double knockout limb buds, and SALL4 is expressed in the ; double knockout limb buds. These results indicate that , , and genes downstream of , regulate femur and tibia development. In the autopod, we show that negatively regulates Hedgehog signaling, which allows for development of the most anterior digit. Collectively, our study illustrates genetic systems that regulate development of the proximal-anterior skeletal elements in hindlimbs.